A better understanding of cell mediated immunity in man. Particularly, normal or abnormal immunologic mechanisms involved in epithelial and lymphoid malignancies, auto-immune disease, homograft rejection and allergic contact dermatitis. Basic studies on the function and correlative morphology of lymphocytes and macrophages involved in a blastogenic response to specific antigen and foreign tissue. Identification and characterization of soluble mediators produced in stimulated and unstimulated human leukocyte cultures. Characterization of the abnormal blastogenic responses found in certain diseases, particularly lymphoid malignancies. The necessity of both lymphocytes and macrophages in blastogenic responses in vitro has been elucidated and the lymphocyte has been identified as the cell which determines the immunologic specificity of the blastogenic response to antigens. A soluble mediator, released by macrophages, has been found to be an essential requirement for the blastogenic response to antigens and foreign tissue. This factor has been isolated and partially characterized.